Ferritin in mollusks: structural diversity and physiological functions

Ferritin, a protein ubiquitously found in living organisms, is well known for its major role in iron homeostasis. However, recent studies in invertebrates have revealed that it possesses diverse physiological functions beyond iron homeostasis. Especially in mollusks, ferritin has been suggested to be involved in functions such as restricting iron availability to pathogens during immune responses, mediating iron transport to specific tissues via hemolymph, and contributing to the formation of mineralized tissues, such as shells and radulae. Furthermore, it has been demonstrated that mollusks possess not only the cytoplasmic ferritin found in vertebrates, but also a secretory ferritin, which contains a signal peptide. This review provides a comprehensive overview of molluscan ferritin, summarizing the broad aspects of its molecular structure and physiological functions.